1. Field of the Invention
The present invention relates to a vehicle engine mounted on a body frame, in which a starter motor and a speed sensor for detecting the vehicle speed from the rotation of a gear in a transmission are mounted to an upper surface of a crankcase supporting thereon a crankshaft, an input shaft of the transmission, and an output shaft, disposed on the rear side of the input shaft, of the transmission.
2. Description of Background Art
A vehicle engine is disclosed, for example, in Japanese Patent No. 3994149 that includes a starter motor and a speed sensor for detecting the vehicle speed.
In the vehicle engine disclosed in Japanese Patent No. 3994149, a crankcase is composed of an upper case half and a lower case half into which the crankcase is divided in the upper and lower sides. A crankshaft and an input shaft and an output shaft of a transmission, which are laid out on one horizontal plane, are held between the upper and lower case halves. In addition, a starter motor is mounted to a portion, directly above an intermediate position between the crankshaft and the input shaft, of an upper surface of the upper case half. Further, a speed sensor is mounted to a portion, directly above the input shaft, of the upper surface of the upper case half.
In such a configuration as set forth above, the division of the crankcase into the upper and lower case halves makes it necessary for the crankshaft, the input shaft and the output shaft to be laid out on one horizontal plane. In addition, the arrangement of the starter motor at a portion, directly above an intermediate position between the crankshaft and the input shaft, of the crankcase makes it difficult for the crankcase to have a compact form. In addition, since the speed sensor is disposed at a portion directly above the input shaft which is comparatively near the cylinder, the speed sensor is liable to be influenced by the heat generated by the cylinder.